(20 June 1667–9Dec. 1669)
Born at Pistoia on 28 Jan. 1600, of a noble family which derived its wealth from sheep-farming, Giulio Rospigliosi studied liberal arts at Rome with the Jesuits, and then theology and law at Pisa. With the patronage of the Barberini, who admired his artistic flair, and of Urban VIII himself he rose steadily in the curia from 1624 to 1644, when he was appointed titular archbishop of Tarsus and given the responsible post of nuncio to Spain. Leaving Madrid in Jan. 1653 he was made governor of Rome during the sede vacante after Innocent X's death, while the new pope, Alexander VII, appointed him secretary of state and cardinal priest of S. Sisto on 9 Apr. 1657. In this capacity he managed, in spite of the hostility to Alexander of the powerful minister Cardinal Mazarin (1602–61) and Louis XIV (1643–1715), to retain the esteem of the French court. On Alexander's death he therefore had strong French backing; since Spain also favoured him, and the cardinals wanted a pontiff capable of healing the rift between Paris and Rome, his election was assured. Assuming a name indicative of a policy of appeasement, he almost wholly broke with the traditional nepotism, and assigned his relatives only modest and moderately profitable offices.
Much of Clement's short reign was spent in resolving already existing tensions. Thus when Spain recognized (Feb. 1668) the independence of Portugal, he felt able to settle the confused ecclesiastical situation in that country by at last filling the numerous vacant sees. Much more important was the relaxation of relations with France. A humiliating inscription admitting the guilt of the papal soldiers which Louis XIV had forced Alexander VII to set up in Rome was removed; but Clement in return had to allow the French crown a free hand in church appointments. Again, while it flattered him to play a role in the negotiations which ended the War of Devolution (1667–8) between France and Spain, he was no match diplomatically for Hugues de Lionne (1611–71), Mazarin's brilliant successor as French foreign minister, and the peace of Aachen (2 May 1668) left in France's hands the fortified towns in Flanders it wanted. It was also de Lionne who was the true architect of the ‘Clementine Peace’ (Feb. 1669), which brought a temporary respite to the agitation over Jansenism. A minority of Jansenists, including four bishops and the nuns of the Jansenist convent of Port-Royal south-west of Paris, still refused subscription to the formulary condemning five propositions from Cornelius Jansen's Augustinus which Alexander VII imposed in Feb. 1665, but as a result of discussions between de Lionne and the papal nuncio Clement was prevailed on to accept (19 Jan. 1669) the recalcitrant bishops' subscription in spite of its being hedged around with qualifications to which he had to turn a blind eye. It was in fact a victory for Louis XIV, who considered the Jansenists a threat to the unity of his kingdom; and it soon became apparent at Rome that the ‘Peace’ was being interpreted as a sign of the church's weakness in the face of French pressure.